Of Mice and Men

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Stanford University researchers have recently developed a new technique that makes skin temporarily transparent using a popular dye found in snacks, such as Doritos.

As part of a new study, scientists applied a solution containing the FDA-approved dye FD&C Yellow 5 – also known as tartrazine – on the skin of a sedated mouse.

Within five minutes, they could see everything under its skin, such as intricate blood vessels, a beating heart and the fine structures of muscle fibers in limbs.

“You could see through the mouse,” Adam Wax, a program officer at the National Science Foundation that funded the study research, told the Washington Post. “I’ve been working in optics for 30 years, and I thought that result was jaw-dropping.”

The team explained in their paper that the dye’s almost-magical properties are based on the simple science of optics: The process works by altering how light interacts with the skin.

Normally, skin scatters light due to differences in the refractive index of its components, such as water and lipids. And usually, light scatters in many directions when it passes through the body because it bounces off different things, such as fluids and proteins, making it hard to see through.

The team predicted that certain molecules could change how tissues scatter light, so they opted to test the food dye’s properties.

When they soaked raw chicken in a tartrazine solution, it became see-through as more dye was used. Rubbing this solution on mice’s skin made their internal organs visible, as the tartrazine reduced light-scattering and made the tissue appear clear.

And the substance wasn’t toxic for the animals: It caused no damage to the tissue and it could be rinsed off with water, senior author Guosong Hong said in a statement.

Hong said the discovery could revolutionize healthcare and future medical tests.

“This could have an impact on healthcare and prevent people from undergoing invasive kinds of testing,” said Hong. “If we could just look at what’s going on under the skin instead of cutting into it, or using radiation to get a less than clear look, we could change the way we see the human body.”